Lifeless ice? At first glance, the cryosphere – including all frozen water on Earth – appears to comprise vast, cold expanses devoid of biology. However, even the most remote, hostile and unlikely icy locations in both hemispheres have been found to harbour diverse and active microbial life. It is hard to imagine ice offering many viable places for microbes to exploit; but liquid water and energy sources exist beneath, within, and especially on the surfaces of glaciers and ice sheets. Research has shown us that not only are ice-dwelling microbial communities crucial stores of biodiversity, they might be important amplifiers of global climate change. The area...